Floating roof storage tank



PH'H 20, 19448. H. c. BOARDMAN 2,439,792

FLOATING ROOF STORAGE TANK Filed Das. 29, 1945 Patented Apr. 20, 1948 2,439,792 FLoATiNG noot` STORAGE TANK 'Harry C. Boardman, Chicago Bridge & Ir of Illinois Chicago, Ill., assignor to on Company, a corporation Application December 29, 1945, serial No. 638,228 c claims. l(ci. 22o-a) This invention relates to a storage tank and particularly to a tank used for storing fluids such as volatile liquids.

When volatile liquids are to be stored there is always danger of losses due to evaporation of the liquid. There are also explosion and lire hazards if the vapors are of an explosive ty-pe. Among the types oi tanks used for storing volatile liquids is the floating roof tank wherein the roof floats on top of the liquid and within the conilnes of a shell. In tanks of this type the roof is constructed with pontoons so as to give the roof added buoyancy, and the roof is also provided with a seal to close oil the area between the edge of the floating roof and the side of the shell. These tanks are somewhat bulky and expensive to build. `Often the stored liquid volatilizes and the vapors gather under the roof, tending to get it out of balance. In floating roof tanks there is also danger that the vapors will escape around the edge of the roof, especially if the seal becomes worn.

I have invented a new type storage tank for storing volatile liquids wherein the losses on illling, emptying, and standing storage are substantially eliminated. The new tank permits the use of a ilxed weather roof without danger of any explosive mixture being formed beneath the weather roof. The new tank comprises a su-bstantially cylindrical shell, weather roof xed to the top of the shell, a at floating roof within the s-hell, a flexible impervious sealing member connecting the floating roof to the bottom of the tank to dene a storage space under the floating roof, a portion of sealing liquid between the sealing member and the shell, a portion of sealing liquid in the bottom of the storage space, and means connecting the two portions of sealing liquid together. The sealing liquid has a specific gravity greater than that of the liquid to be stored. Filling and emptying means are provided in communication with the storage space at a point above the greatest height of the sealing liquid in the bottom of the storage space.

The new tank will have no evaporation losses either on standing storage or on filling and I emptying the tank. No water, snow, or the like can gather on the iloating roof, as it is protected by a xed weather roof. 'I'here is no seal between the floating roof and the shell other than the sealing liquid between the sealing member and the shell. Because the roof does not depend upon its own buoyancy to float there is no necessity for vpontoons, reinforcing trusses or drains, all of which are needed on the ordinary floating ing roof roof. There is no vapor mixed with air under the iloatlng roof or the ilxed weather roof to create ilre and explosion hazards. As there is no abrasion of the inside oi' the shell this surface may be kept painted so that rust will not form and drop to the bottom to clog the pumps, as sometimes happens with ordinary floating roofs.

'Ihe invention will be described as related to the embodiment shown in the accompanying drawings. Of the drawings Fig. 1 is a plan view of a storage tank embodying the invention with portions broken away for clarity of illustration; and Fig, 2 is a vertical section taken along line 2-2 of Fig. 1.

The storage tank shown in the accompanying drawings com-prises a substantially cylindrical shell Ill, a fixed weather roof II thereover, having a depending skirt I2 beyond floating roof I3 therein, a substantially cylindrical, flexible sealing member I4, attached to the edge of the iloating roof I3 and to the bottom I5 of the tank, a portion I6 of sealing liquid between the sealing member I 4 and the shell I0, and a second portion I1 of sealing liquid over the bottom I5 and within the sealing member I4.

The weather roof II is supported on the shell i0 by means of a plurality of spaced posts I8 attached to the top of the shell and supporting the weather roof.l The space between the top of the shell and the weather roof is covered by a screen I9. Any other type of opening besides the screen may be provided to permit flow of air around the top of the shell I0. The depending skirt I2 serves as a shield to the like from blowing in through the screen I9.

The floating roof I3 has a ilat bottom and is provided with an upstanding edge flange 20. The ilexible sealing member I4, which may be a fabric impregnated with a flexible impervious material, is attached to the edge of the floating roof as by boltlng the top edge of the sealing member to the bottom of the flange 20 by means of bolts 2i. The flexible sealing member is substantially cylindrical in shape and has a diameter slightly greater than the diameter of the float- I3, but smaller than the diameter of the shell i0. The sealing member is substantially as long as the maximum storage space desired, and has its .bottom end attached in sealing contact with the bottom I5 of the tank.

The portion I 6 of sealing liquid between th-e sealing member I4 and the shell I 0 is preferably the same liquid as that portion I1 at the bottom of the storage space 22. The sealing liquid is of greater specic gravity than the liquid the shell, a ilat prevent snow, rain, dirt, and

to be stored within the storage space. Means are provided connecting the two portions I8 and I1 of sealing liquid, and this means may be a bypass pipe 23 in communication with both portions of sealing liquid. Other means may also be used. such as holes provided in the bottom of the sealing member i4.

Filling and emptying means are provided communicating with the storage space 22 at a point above the highest possible level of the portion l1 of sealing liquid at the bottom of the space. This means may be an inlet and outlet pipe 24.

The level of the two portions of the sealing liquid will depend upon the weight of the floating roof i3, the weight of the sealing member i4, the difference between specific gravitles of the sealing liquid and the stored liquid, and the amount of stored liquid within the storage space. The system may be so designed that the level of sealing liquid between the sealing member I4 and the shell I is always substantially at or just below the bottom of the floating roof i3. As liquid to be stored is pumped into the storage space 22 the floating roof I3 rises within the shell l0, and the quantity of sealing liquid at the bottom of the storage space is decreased, while the quantity of liquid outside the sealing member i4 is increased. When stored liquid is withdrawn the floating roof will fall and the conditions will be just the opposite. When substantially all stored liquid has been withdrawn the floating roof will be near the bottom of the tank and most of the sealing liquid will be in the bottom of the storage space. It is necessary that the pipe 24 extend above the maximum height of the sealing liquid in the bottom of the storage space in order that no sealing liquid will be withdrawn with the stored liquid.

As can be seen from the above description, any vapor formed from the stored liquid will collect beneath the floating roof I3 and will be held by the sealing member i4. In this respect the storage tank constitutes both a'liquid and gas container. The same principles as used in constructing a storage tank for volatile liquids may also be used in constructing a similar tank for the storage of gases.

Having described my invention as related to one embodiment of the same it is my intention that the invention be not limited by any of the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. A storage tank comprising an outer shell, a bottom therefor, a floating roof smaller than the shell and located within the shell, a flexible sealing member connecting the floating roof to said bottom to define a storage space under said floating roof, a portion of sealing liquid between the sealing member and the shell, a portion of sealing liquid in the bottom of the storage space, said portions of sealing liquid having specific gravities greater than that of the stored liquid, means connecting that portion of sealing liquid outside the sealing member with that portion at the bottom of the storage space, and filling and emptying means communicating with 4 the storage space ata point above the greatest height of the sealing liquid in the bottom of the storage space.

2. The storage tank of claim 1 wherein the sealing liquid in both portions is the same.

3. The storage tank of claim 1 wherein the lling and emptying means extend through the bottom of the tank.

4. A storage tank for liquids comprising an outer shell, a bottom therefor, a iioatin roof smaller than the shell and located withi the shell, a flexible sealing member connectin the floating rooi to said bottom to define a storage space under said floating roof, a portion of sealing liquid between the sealing member and the shell, a second portion of the same sealing liquid in the bottom of the storage space, said sealing liquid having a specific gravity greater than that of the stored liquid, means connecting that portion of sealing liquid outside the sealing member with that portion at the bottom of the storage space, and filling and emptying means extending through the bottom of the tank and communicating with the storage space at a point above the greatest height of the sealing liquid in the bottom of the storage space.

5. The storage tank of claim 4 wherein the floating roof is of circular shape and the iiexible sealing member is a cylinder of approximately the diameter of the iioating roof.

6. A storage tank for liquids comprising `an outer shell, a bottom therefor, a weather roof over the shell, air openings between the weather roof and the shell, a floating roof smaller than the shell and located within the shell, a substantially cylindrical flexible sealing member of approximately the diameter of the floating roof having one end attached to the floating roof at substantially the edge thereof and the other end attached to the bottom of the tank substantially beneath the iirst end to define a storage space between the floating roof and the bottom of the tank and within the sealing member, a portion of sealing liquid between the sealing member and the shell, a second portion of the same sealing liquid in the bottom of the storage space, said sealing liquid having a specific gravity greater than that of the liquid to be stored, means connecting that portion of sealing liquid outside the sealing member with that Aportion at the bottom of the storage space, and filling and emptying means extending through the bottom of the tank and communicating with the storage space at a point above the greatest height of the sealing liquid in the bottom of the storage space.

HARRY C. BOARDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Wiggins Oct. 1, 1946 

